SIP 180 Ringing vs 420 Bad Extension
SIP 180 (Ringing) is a 1xx Provisional response, while 420 (Bad Extension) is a 4xx Client Failure response. 180 indicates that the UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end. In contrast, 420 means that the server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the unknown extensions.
Descripción
The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
Cuándo lo verás
During call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
Cómo solucionarlo
No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings.
Descripción
The server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the unknown extensions.
Cuándo lo verás
When the request includes a Require header with SIP extensions that the server does not support.
Cómo solucionarlo
Check the Unsupported header in the response. Remove the unsupported extension from the Require header or make it optional via Supported.
Diferencias clave
180 is a 1xx Provisional response, while 420 is a 4xx Client Failure response.
SIP 180: The UA receiving the INVITE is trying to alert the user. This response is used to initiate local ringback tone at the caller's end.
SIP 420: The server did not understand the protocol extension specified in a Require or Proxy-Require header. The Unsupported header lists the unknown extensions.
You encounter 180 when during call setup when the callee's phone is ringing. You should hear a ringback tone after receiving this response.
You encounter 420 when when the request includes a Require header with SIP extensions that the server does not support.
Cuándo usar cada uno
For 180 (Ringing): No fix needed — the callee's device is ringing. If the call never connects after ringing, check the callee's device or call forwarding settings. For 420 (Bad Extension): Check the Unsupported header in the response. Remove the unsupported extension from the Require header or make it optional via Supported.